The present invention relates to a dry, granular, bleaching composition comprising a peroxyacid compound, diperoxydodecanedioic acid, and sufficient buffering agent to control the pH of an aqueous oslution of the bleach in the range of 8.7 to 9.5.
Peroxygen bleaching agents in general and peroxyacid compounds in particular have long been recognized as effective bleaching agents for use when the adverse color effects of harsh active bleaching agents cannot be tolerated. See, for example, Canadian Pat. No. 635,620, Jan. 30, 1962, to McCune. The peroxyacids used have included aliphatic acids as disclosed in McCune, as well as aromatic acids such as diperoxyisophthalic acid disclosed in U.S. Pat. No. 3,770,816, Nov. 6, 1973, to Nielsen. Use of these agents has necessitated finding adequate solutions to a number of problems. Included in the types of problems heretofore recognized with peroxyacids are the tendency of such materials to undergo exothermic decomposition, the loss of available oxygen from peroxyacids as the result of contact with moisture and heavy metals and the degradation of peroxyacids as the result of contact with alkaline agents.
It has also been discovered that, although diperoxyacids in general are milder to fabrics than chlorine-containing bleaches, they are not entirely free of fabric damage problems. The recognition of certain pinpoint color damage problems with peroxyacids in general is disclosed in Belgium Pat. No. 814,938, Nov. 13, 1974, to Gougeon et al. With the peroxyacid of interest of the present invention, diperoxydodecanedioic acid, nylon color damage can be fairly severe. This damage is due to the bleach active being adsorbed/absorbed onto/into the nylon fiber.
The present inventor has discovered that the above-mentioned nylon color damage can surprisingly be reduced by maintaining the pH of the wash solution in which the bleach is used within a certain high pH range, 8.7 to 9.5. It is theorized, although such theory is not to be considered binding, that at the pH's of the present invention the diperoxyacid is more completely ionized and the peroxyacid anion is much less substantive to the nylon fiber. The aforementioned Belgium patent does not suggest that optimized performance (low nylon color damage with high bleach effectiveness) of diperoxydodecanedioic acid would occur in the pH range given above.
Accordingly, it is an object of the present invention to provide an improved fabric bleaching composition having superior bleaching performance.
It is a further object of the present invention to provide a superior method of bleaching fabrics.
These and other objects will become apparent from the description which follows.
As used herein, all percentages and ratios are by weight unless otherwise specified.